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National Research Council (US) Committee on Scientific Issues in the Endangered Species Act. Science and the Endangered Species Act. Washington (DC): National Academies Press (US); 1995.

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Science and the Endangered Species Act.

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4The Role of Habitat Conservation and Recovery Planning

The Importance of Habitat

Habitat is the physical and biological setting in which organisms live and in which the other components of the environment are encountered (Krebs, 1985; Jones, 1987). The concept of habitat is critical to modern ecology and was adopted and promulgated in some of the earliest treatises and texts (Elton, 1927; Clements and Shelford, 1939); habitat is a basic requirement of all living organisms (e.g., McNaughton, 1989). Habitat is one of the four components of a species' environment, along with climate variables, nutrients, and other interacting organisms (Andrewartha and Birch, 1954). The fact that habitat serves a multitude of organisms is critical to understanding its full role in the Endangered Species Act. Many species have not been classified, nor their status determined. Our knowledge of species is too limited, and the species deserving of endangered or threatened status too numerous, to list all that might merit it in a time frame adequate to protect them. The number of unclassified living species is thought to be from two to ten times the number that have been identified and named (Wilson, 1992). Although this gap in knowledge is greatest in the tropics, invertebrates are also incompletely described in temperate habitats, particularly for soil organisms and many marine groups. Even among named species in the United States, genetic diversity of subspecies and of vertebrate population segments is poorly understood, except for relatively few vertebrates that have received special attention because they are commercially or recreationally important. Prospects are scant for a significant, near-term change in this information gap, because the task is so immense, and there are few specialists for many plant or invertebrate taxa. Therefore, broad, ecosystem-based conservation measures that depend neither on taxonomic knowledge nor on the determination of listing status of individual species are also needed to prevent species extinction (see Chapter 10).

Fortunately, the distribution of habitats on which species diversity depends is somewhat better understood. In California, for example, reliable inventories document the loss of habitat and the extent of many valuable remnants, including coastal and inland wetlands, native coastal dunes, coastal sage scrub, oak woodlands, vernal pools, and free-flowing rivers (Jensen et al., 1993). Many endangered species are also found in California, as the Endangered Species List (50 CFR 17.11 & 17.12) shows. The relationship, nationwide, between vanishing habitats and vanishing species is well documented (see Chapter 2).

Based on studies of the relationship between habitat area and several groups of organisms, a simple and fairly general ecological relationship has emerged: species diversity is positively correlated with habitat area (McArthur and Wilson, 1967; Pianka, 1978). The relationship is Image img00005.jpg where S is the number of species, A is the area of the habitat, and C is an empirically determined multiplier that varies from place to place and among taxa. The exponent Image img00004.jpg varies according to topographic diversity and isolation of the habitat; Image img00004.jpg is usually larger for islands (around 0.3) than for mainland habitats (often less than 0.2). A corollary of this relationship is that if habitat is substantially reduced in area or degraded, species will be lost. The loss is not linear; a loss of 90% of the habitat results in the estimated loss of 30%-60% of the dependent species (Groombridge, 1992). The species loss might be even greater than 30%-60% for at least three reasons. First, we lack sufficient taxonomic and ecological understanding of many taxa that might have demands on habitat area quite different from those of the more intensively studied taxa. Also, lack of knowledge about a taxon can lead to an incorrect evaluation of the species-area relationship for it, because it can lead to misidentification of species. Second, many species-area relations were developed for nonmigrant species, tropical species, and true island populations—conditions that strictly apply to few North American taxa. Third, habitat can be altered in many ways, and the effects of most of these alterations on species numbers have not been studied.

Despite uncertainties in the actual mathematical relationship between habitat size and the number of species in that habitat, there is no disagreement in the ecological literature about one fundamental relationship: sufficient loss of habitat will lead to species extinction (see Chapter 2). And habitat protection is a prerequisite for conservation of biological diversity. Habitat protection is essential not only to protect those relatively few species whose endangerment is established, it is also in essence a pre-emptive approach to species conservation that can help to avoid triggering the provisions of the Endangered Species Act.

Loss of habitat is a major factor in species extinctions when the cause of extinction is known. Groombridge (1992) provided a table showing that for animals with known causes of extinction, hunting (mostly unregulated) caused extirpation of 23%, introduced animals caused 39%, and habitat loss accounted for the loss of 36%. Habitat loss has been more important as a recent cause of extinction of terrestrial than marine species to date and probably accounts for more than 36% of the extinctions where the cause is unknown, because extirpation due to unregulated hunting is easily documented.

Habitat loss places additional pressures on endangered species management because where the amount of habitat available is limited, protection or maintenance of the present condition of a habitat for one species can adversely affect another (see Chapter 6). For example, boundaries or edges between different habitat types (gaps or openings) favor some wildflowers and other desirable plants (Whitford, 1949; Gilbert, 1980), but large, unbroken tracts of habitat favor other species. When the amount of habitat available is limited, the design of optimal combinations of mosaics of distinct habitats across landscapes becomes a major challenge to managers.

The Role of Habitat Conservation Under the ESA

The role of conserving habitat for endangered species has been recognized since the first federal endangered species legislation. For example, the Endangered Species Preservation Act of 1966 (P.L. 89-699), stated, "It is . . . the policy of Congress that the Secretary of Interior, the Secretary of Agriculture, and the Secretary of Defense . . . shall preserve the habitats of such threatened species on lands under their jurisdiction" (Section 1(b)). Over time, as our knowledge of species requirements has grown, the legislation has evolved from the regulation of harvest and trade in species to the protection of habitat. The stated purposes of the current ESA are to conserve endangered species "and the ecosystems on which they depend" (16 U.S.C. 1531), a clear mandate linking successful conservation of species to the habitats that they require. This linkage is entirely appropriate scientifically.

The ESA provides throughout for the identification and protection of habitat. The first statutory consideration for the listing of species as threatened or endangered is "the present or threatened destruction, modification or curtailment of its habitat or range" (§1533). Section 4 of the act further requires the designation of a species' "critical habitat" concurrently with the listing of a species, unless earlier listing is "essential to the conservation" of the species (§1533(b)(6)(C)(8)) or unless the designation of critical habitat is not ''prudent" or "determinable" (§ 1533(a)(3)). Critical habitat designations are, "to the maximum extent practicable," to be accompanied by "a brief description and evaluation of those activities (whether private or public) which, in the opinion of the Secretary, if undertaken may adversely modify such habitat, or may be affected by such designation" (§1533(b)(6). Critical habitat is to be designated "on the basis of the best scientific data available and after taking into consideration the economic impact, and any other relevant impact, of specifying any particular area as critical habitat" (§1533(a)(3)). (Critical habitat designation is not mandated for the species listed before 1978, when these provisions were added. To date, critical habitat has been designated for less than 20% of all species listed in the United States. Furthermore, the ESA provides for exclusion of areas from critical habitat if it is determined that "the benefits of such exclusion outweigh the benefits of specifying such area," unless failure to designate the area "will result in the extinction of the species concerned" (§1533(b)(2)).

Section 7 requires federal agencies to consult with the Fish and Wildlife Service (FWS) and the National Marine Fisheries Service (NMFS) to ensure that federal actions are not likely to jeopardize the continued existence of listed species or result in "the destruction or adverse modification" of their critical habitat (§1536). Habitat modification gives rise to the vast majority of these consultations, nearly all of which are resolved informally or with modifications that allow projects to proceed as planned.

Sections 9 and 10 of the act have extended the review of habitat modification to nonfederal, private development. (However, recent court decisions have left uncertain the validity of FWS regulations that state that habitat modification constitutes "take.") Section 9 prohibits "take" of a listed species, a term described elsewhere in the act as, among other things, "harm" to a species. Early FWS regulations described this harm to include "significant habitat modification or degradation" that "kills or injures wildlife" (50 CFR 17.31 )). The act's application to habitat modification by private parties led to the development of early conservation plans in California, a process endorsed by the Congress in 1982 with the additions to Section 10. Section 10 (a) currently requires "habitat conservation plans" of private parties seeking to secure an "incidental take" permit (unintentional take) for listed species (§1539(a)(2)).

One exception to the habitat conservation planning requirements of Sections 9 and 10 is worth noting. Although Section 7 constrains federal agencies from jeopardizing plant and animal species, no such constraints are imposed on private parties for the incidental taking of listed plants. Private parties are forbidden only from "removing" or "maliciously" damaging or destroying endangered plants found either on federal lands or under the protection of state law (§1538(a)(2)). However, plants are covered by habitat conservation plans in that the Section 10(a) permit requires a consultation under the Section 7 requirements.

Recovery planning under Section 4 of the act is likewise keyed to habitat protection. Each recovery plan is to include "site-specific management actions as may be necessary to achieve the plan's goal for the conservation and survival of the species" (§1533(f)(1)(B)). Because most species are endangered due to loss or degradation of habitat, site-specific actions should include identification, restoration, and management of habitat.

Habitat acquisition for endangered species has also been a part of the federal program from its beginnings. Later amendments to the ESA have augmented the authority and funding for this effort, but acquisition has not kept and cannot keep pace with the number and size of the affected habitats or the modification and degradation that they face.

In summary, habitat protection has always been an important component of endangered species programs. As our experience with endangerment and recovery has increased, habitat has become the central ingredient, and the ESA, in emphasizing habitat, reflects the current understanding of the crucial biological role habitat plays for species.

Critical Habitat and Federal Activities

Section 7 imposes a special requirement on federal agencies to ensure that their activities are "not likely to . . . result in the destruction or adverse modification of habitat of [listed] species which is determined by the Secretary, after consulting as appropriate with affected States, to be critical . . .". Critical habitat is a valid biological concept. The requirement of Section 7 corresponds to the understanding of conservation biology that certain habitat is essential for species survival. Habitat critical to species can be identified from the knowledge of species and ecosystems as objectively and scientifically as a species can be identified for listing. However, as is the case with listing decisions on many rare species, detailed information needed to designate critical habitat might be lacking. Simple occurrence of a species within a habitat does not necessarily mean that the habitat is required by the species (Van Horne, 1983) or that the amount and quality of habitat might be considered "critical." But that a species is absent from a given habitat does not mean that the habitat is not critical to the persistence of the species (see Chapter 5). Identification of the relationship of a species to habitat and the determination of what is critical to the long-term survival of that species are high priorities for long-term conservation. The complexity of designating critical habitat will vary by species, but designation should be possible in many cases. Mechanisms exist to uncouple critical habitat designations from listing when they need additional investigation and would otherwise cause delay. Mechanisms also exist to withhold these designations where they are not "determinable" or otherwise "prudent." That nearly 80% of all species listed do not have critical habitat designations is a cause for concern.

Survival Habitat

The question has been raised whether critical habitat should be determined at the time of listing or whether it should be deferred to the time of recovery planning. The advantages of early designation include the provision of some "early warning" to all parties, and in particular, the affected federal agencies, that such areas are to be treated with particular caution. Designated habitat is protected by a more objective standard ("no adverse modification") than that provided for threats to species ("no likelihood of jeopardy") in that adverse habitat modifications are more amenable to objective measurement and quantification than are the many factors that might contribute to jeopardizing the survival of a species. The standard of habitat protection provides an important point of focus for those outside of government, including the scientific community, to help protect areas at least until recovery plans are developed that will clarify the needs of endangered species and provide more fully for their recovery. Importantly, critical habitat designation can be beneficial to other listed and nonlisted species living in the designated area, especially for those species for which satisfactory long-term recovery plans have not been implemented.

The committee recognizes that because of public concern over economic consequences, the designation of critical habitat is often controversial and arduous, delaying or preventing the protection it was intended to afford. Because critical habitat plays such an important biological role in endangered species survival, we believe that some core amount of essential habitat should be designated at the time of listing and should be identified without reference to economic impact. We recognize, however, that economic review may need to remain linked to critical habitat determination in the ESA, and that determination of areas essential to the recovery of a species, including areas not currently occupied by that species, can be especially complex. Hence, we recommend designation of survival habitat for endangered species as follows:


Survival habitat would be designated at the time of listing, unless insufficient information were available or harm to the species would occur. For this purpose, survival habitat would mean that habitat necessary to support either current populations of a species or populations that are necessary to ensure short-term (25-50 years) survival, whichever is larger.2 Survival habitat would receive the full protection that the Endangered Species Act accords to critical habitat, and the adverse modification standard of Section 7 (a)(2) would apply. No economic evaluation would be conducted. The purpose of this requirement is to preserve scientific and management options until recovery plans are in place and effective.


The designation of survival habitat (and its protection under the ESA) would automatically expire with the adoption of a recovery plan and the formal designation of critical habitat. This underscores the emergency and temporary nature of survival habitat. It is intended to be a way of avoiding delays and providing immediate protection while a more comprehensive evaluation of habitat requirements is performed, not as a substitute for critical habitat designation. Expedited review and designation of survival habitat should be made for each currently listed species whose critical habitat has not yet been determined, unless recovery planning, including critical habitat designation, is expected within the period required for survival habitat designation.


Subsequent recovery planning would include designation of critical habitat as currently defined in the ESA (including economic evaluation) to include areas necessary for species recovery.

Because in our recommendation essential survival habitat is identified without reference to economic impact, and because it might not be sufficient to ensure long-term survival and recovery of endangered species, the committee views it as an emergency, stop-gap measure until critical habitat can be designated and a recovery plan can be completed, not as a substitute for those measures. To avoid harm that indefinite delays in designating critical habitat and formulating recovery plans might cause to economic interests and to the endangered species itself, the implementation of this recommendation needs to include ways of preventing those delays from occurring.

Private Activities and Habitat Conservation Planning

Endangered species are found across North America, and slightly more than 59% of land in the United States is privately owned (about 8% is under state and local ownership and about 33% is federally owned (NRC, 1993)). Clearly, a program that targets only the portion of the United States that is under federal control will not prevent species extinction. Habitat conservation planning under Section 10 and, more recently, Section 4(d), has addressed species protection on private lands. Two examples of habitat conservation planning are described below.

Habitat-Conservation Plans

In Section 7 of the ESA, Congress offered relief from Section 9 prohibitions against taking endangered species where the government's actions were "not likely to jeopardize the continued existence of any endangered or threatened species." Similar relief was not available to nonfederal parties when federal permits were not required for development or other activities. In its 1982 amendments to the ESA, Congress provided non-federal parties the possibility of obtaining legal exemption from Section 9 prohibitions against take of endangered species (and, by regulation, of threatened species). It amended the ESA to provide private nonfederal parties "incidental take" permits under Section 10(a), if a habitat conservation plan (HCP) is submitted that, when implemented, "will, to the maximum extent practicable, minimize and mitigate the impacts of such taking" and "not appreciably reduce the likelihood of survival and recovery of the species in the wild'' (16 U.S.C. 1539(a)(2)(A)).

Congress also intended to provide a framework that would encourage creative partnerships between the private sector and local, state, and federal agencies in the protection of endangered species and habitat conservation. The legislators pointed to the model of the San Bruno Mountain HCP,3 developed by private landowners and local, state, and federal government agencies to conserve the endangered mission blue butterfly (Plebejus icarioides missionensis) and several co-occurring species in coastal California. Although it focused on listed and candidate species, the HCP addressed the San Bruno Mountain ecosystem as a whole, including its diversity of species and habitats. The plan included protection of open space and habitat diversity; management, including control of exotic species and habitat restoration; protection of sensitive species during project construction; funding of plan activities; and assurances to the private sector that new requirements would not be imposed after the plan was accepted (Thornton, 1991). Most of the grassland habitat of the butterfly was protected, and its population more than a decade later is as large as it was before the plan was implemented.

The model had its second test in southern California, where the threatened Coachella Valley fringe-toed lizard (Uma inornata) survived in remnant sand-dune habitats, at risk from suburban expansion around Palm Springs. Challenged to preserve both dune habitat and distant montane sources of sand, FWS ultimately agreed to a reserve system of nearly 17,000 acres. However, this habitat constitutes barely 10% of the occupiable habitat that existed at the time the HCP was initiated, and little is known even now about what characteristics of the lizard's biology cause its dramatic population fluctuations and put it at risk of extinction (Beatley, 1994).

These plans have had few imitators. Several promising regional HCPs have collapsed before completion. Two of the more notable ones are the North Key Largo (Florida) HCP, designed to conserve the American crocodile (Crocodylus acustus), the Key Largo woodrat (Neotomafloridana smalli), the Key Largo cottonmouse (Peromyscus gossypinus allapaticola), and other species; and, very recently, the Balcones Canyonlands HCP (near Austin, Texas), which focused on the black-capped vireo (Vireo antricapillus) and the golden-cheeked warbler (Dendroica chrysoparia), among other species and their habitats.

Although FWS provides detailed guidelines on administrative procedures for developing HCPs (FWS, 1990; 1994), its directives in the application of biological data to plan development are very sparse. The guidelines state that on request, FWS will indicate whether the biological data are adequate to proceed with the other elements of this process. If desired, FWS will recommend the number, type, scope, and general design of studies needed to provide acceptable data to develop the conservation plan. FWS, however, has had remarkably few opportunities to exercise this offer, because completed HCPs have been so few.4

Critics have argued that HCPs demand inordinate amounts of time, human resources, and money, and they should be avoided if possible (e.g., Mann and Plummer, 1995). Consultants encourage private landowners to use any federal "hook" (i.e., relationship to some federal activity) possible to avail themselves of the more expeditious Section 7 consultation process. Reasons for the limited number of completed HCPs are myriad, but at the very least, increased funding is necessary to upgrade the active role of FWS in the process. Furthermore, agency staff need the biological guidelines that FWS offers to those who seek permits under Section 10(a). Appropriate guidelines should be developed to assist planners in applying biological data to habitat-conservation planning. They should include much of the agenda discussed in this report under recovery planning, as well as elements from California's Natural Communities Conservation Plan described below. Finally, they should attempt to resolve dilemmas that might arise if the need for ecosystem protection were to conflict with the legal requirement of protection of individual species; in other words, an ecosystem should not fail to receive protection because of the needs of a single species. Wherever possible, HCPs should be regional in scope and should serve multiple species across multiple habitat types. Model programs are in process concerning the scrub community of Brevard County, Florida, and the southern San Joaquin Valley of southern California.

At a minimum, guidance should be offered in (1) development of explicit reserve design and management goals and objectives, (2) identification of techniques and data needed to perform population-viability analysis or equivalent demographic or metapopulation modeling efforts to assess likelihoods of persistence of target species under alternative planning options, (3) description of management options and discussion of how ongoing research and monitoring activities will be used to adjust management in response to changes in population sizes and environmental variables, (4) application of risk analyses in consideration of plan alternatives, and (5) description of how these exercises should be applied in the land-use planning process. Guidelines thus should describe a discrete scientific program for HCPs that will be specific, efficient, and cost-effective (although it will usually be impossible to make HCPs inexpensive).

Recovery Planning

The ultimate goal of the ESA is to recover threatened and endangered species. Recovery is described as "the process by which the decline of a threatened or endangered species is arrested or reversed, and threats to its survival are neutralized, so that its long-term survival in nature can be ensured" (FWS, 1992). The 1978 amendments to the act first required that, following species listing, a recovery plan be developed (§1533(f)). Faced with delays in this part of the planning process and with plans too vague to provide meaningful guidance, Congress has increased funding and provided more detailed requirements for the contents of these plans (§ 1533f(l)(B)). Despite this increased attention, recovery plans are developed too slowly. There appear to be legitimate concerns about the adequacy of recovery plan objectives and commitments to implement them. Plans that involve species of little public interest often sit unimplemented for long periods, especially if they would be expensive to implement (Tear et al., 1993).

The backlog in recovery planning is significant because it is large, and because nearly everything else in the act can be seen as a preliminary measure (e.g., listing) or as protecting the options for recovery plans (e.g., critical habitat designation or consultation). In 1988, more than 10 years after recovery plan requirements were first added to the statute, only 56% of listed species had recovery plans approved, with another 18% in preparation. In 1992, some 61% of species had approved plans, but by the following year the percentage had dropped to 53%, a figure attributable to recent accelerated listing actions. As of March 31, 1995, resource agencies had approved 411 plans covering 513 species, 54% of the 956 U.S. species listed at that time.

A FWS report to Congress (FWS, 1992)—the most recent data available to the committee—evaluated recovery progress as of September 30, 1992, based on the percentage of tasks accomplished for downlisting, delisting, or maintaining current populations for the foreseeable future. Managers had attained greater than 50% of their recovery objectives for only 68 species, while 544 species (77% of listed species, including all recently listed species) had less than 25% of their recovery tasks completed. However, the report noted that 201 species, 28% of the total, were stable and 69 species (10%) were improving.

A review of 314 recovery plans for threatened and endangered species as of 1991 (Tear et al., 1993) concluded that

  • Only about 17% of the plans contained population-size data;
  • Nearly one-third of the plans with population data set recovery goals at or below the population size believed to exist at the time of listing; and
  • Sixty percent of the vertebrates would remain at imminent risk of extinction with about a 20% probability of extinction within 20 years or 10 generations, whichever is longer, even if every population target were met.

In the recovery planning guidelines, recovery planners are asked to adhere to an explicit format that includes (1) an introduction that describes pertinent ecological, genetic, and other information related to the biology of the listed species and threats to it; (2) a recovery objective and criteria to meet the objective; (3) an implementation schedule, including priorities of tasks and cost estimates; and (4) an appendix identifying appropriate reviews of the plan and peripheral but pertinent documents or communications. Recovery plan tasks 1 and 4 are by and large straightforward; unfortunately, tasks 2 and 3 are not, for different reasons.

The guidelines correctly observe that the quantification of "recovery criteria calls for creative thought and developing the criteria may require educated guesswork." Nonetheless, they demand "concise and measurable recovery criteria" that will serve as "the central pillar of the recovery plan." Population viability analysis is the cornerstone, the obligatory tool by which recovery objectives and criteria are identified. Yet the demographic and genetic data necessary to fuel such analyses are lacking for virtually all species for which recovery plans exist, and likewise for those in and awaiting entry into the recovery-planning process.

In the absence of adequate data, "educated guesswork" has and will continue to rule the development of the "central pillar" of recovery plans. Moreover, few scientists agree on the data and analyses that are required to produce a reliable population viability analysis for conservation planning purposes. What most will agree is that many obligatory elements, such as variance in reproductive success, are difficult to quantify and that the time-series data necessary to reduce the confidence intervals around projections from population viability analyses demand long-term and expensive field research. In essence, even to set objectives and criteria for recovery in a scientifically defensible manner (much less to carry them out) will demand resources well beyond those currently available. Nevertheless, many analytical tools that were unavailable to planners in the past now could be used to add greater scientific rigor to recovery plans (see also Chapter 7). However, the recovery guidelines offer no explicit schedule or outline for bringing data to bear in setting recovery objectives or criteria. The committee believes that FWS should convene a working group to develop explicit guidelines for the application of data to the construction of recovery objectives and criteria, with particular emphasis on the estimation of risks and the rational establishment of risk criteria.

Planners would receive general guidance covering at least the following topics:


A habitat-based, in situ approach to recovery that puts ex situ actions (e.g., captive rearing) in their appropriate context.


A logical hierarchical approach to the analysis of available data on the species and its habitats and to the acquisition of additional information on the species of concern and the habitats that support it, including predictions from ecological theory and population dynamics models and inferences drawn from related species.


Guidance for the application of population viability analysis in conservation planning that clearly identifies in planning prescriptions the inherent uncertainty that accompanies such demographic modeling exercises.


An outline that describes in detail future research needs and how that research when completed will contribute to species and habitat management.


An effective monitoring scheme that relates census information to the physical and biotic factors likely to affect population dynamics.

Because prioritizing activities is necessary but difficult, and because estimating cost would be helpful but nearly impossible for typical recovery teams to carry out, the committee recommends that the prioritization and estimation of costs currently called for in recovery planning be reviewed.

Recovery planning remains handicapped by delays in implementation, the scientific validity of objectives, and the uncertainty of application to other federal activities. To be scientifically credible and to increase their likelihood of being successful, recovery plans should consider at least the following questions.

How much of a species' historic range should be protected to ensure recovery or prevent extinction?

Are there critical aspects of a species' life history or ecological and genetic requirements that must be known to successfully implement a recovery plan? Are they known?

What is known about the species' use of and need for corridors among its various populations?

To what degree is a focus on a single species likely to be as successful as an approach that includes the needs of other species in the area, or an ecosystem approach?

A final desired feature is that recovery plans reflecting the best judgment of science from decisions made before listing through consultation and habitat planning bear some relationship to decisions affecting the future of the species. We recommend, therefore, that all recovery planning include an element of "recovery plan guidance," particularly with regard to activities anticipated to be reviewed under sections 7, 9, and 10 of the ESA. To the extent feasible, the guidance should identify activities that can be assumed to be consistent with the requirements of those sections, activities that can be assumed to be inconsistent with them, and activities that require case-by-case evaluation. The guidance should also specify criteria for use in preparing habitat management plans by persons seeking authorization for activities under Section 10 of the ESA and for the planning of federal agencies in furtherance of their Section 7 responsibilities. These measures are fundamental to many recovery efforts.

The real issue is that no recovery plan, however good it might be, will help prevent extinction or promote recovery if it is not implemented expeditiously. Indeed, the failure to implement a recovery plan quickly can also increase the disruption of human activities, through uncertainty, among other causes.

Funding will be required to develop sound recovery plan guidance and the recovery plans themselves. Unfortunately, recovery planning under the ESA has a history of large ideas and little follow-through. Expenditures for recovery have increased in recent years but remain meager compared with the billions of dollars likely to be needed to attain recovery goals for the bulk of listed species (DOI Office of the Inspector General, 1990; Jackson, 1992). The FWS appropriation to support recovery programs was $10.6 million in FY 1990. For FY 1995, it was $39.7 million. More realistic budgets are essential. Mechanisms should be considered to facilitate funding of complex plans, including special funds for plan implementation and funding agreements with affected parties (e.g., private, state, local, tribal, and other agencies).

We also suggest consideration of a new, comprehensive and continuing funding mechanism for developing and implementing recovery programs for listed species. General wildlife and migratory waterfowl programs at the federal and state level have been funded for decades through trusts based on hunting and fishing licenses and the sales of arms and ammunition. Federal restoration programs for hazardous waste sites, abandoned surface mines, and the nation's coastal zone are similarly funded by dedicated revenue sources. Some state acquisition and restoration programs are likewise based on user fees and on real-estate transfers. These earmarked funding sources are widely accepted and successful in providing stable revenue on which long-term planning decisions can be based. Planned programs to recover listed species would benefit enormously from similar support.

The following description of the Natural Communities Conservation Program for the coastal sage-scrub communities of southern California is an example of how many of the recommendations that the committee has provided are being implemented in a program that could serve as a model for better recovery planning and permitting under sections 7 and 10(a).

Natural Community Conservation Program and Coastal Sage Scrub Community of Southern California

Recent listings of the northern spotted owl, desert tortoise, fish species from the Sacramento-San Joaquin delta estuary, and California gnatcatcher have affected economic activity in several regions of California. Secretary of the Interior Bruce Babbitt has advocated new and innovative ways to avoid these "economic train wrecks," favoring approaches that take a comprehensive view of endangered species protection. His strategy for listing the California gnatcatcher by using a special rule under Section 4(d) of the ESA in cooperation with California's Natural Community Conservation Plan (NCCP) allows for moderate economic growth while conservation plans for the gnatcatcher are developed that also consider other unlisted species in the coastal sage scrub.

The goal of NCCP is to conserve healthy functioning ecosystems and the species that are supported by them. The pilot program for this process focused on the coastal sage scrub ecosystem in southern California. Remnant, coastal sage scrub habitats support a diverse assemblage of native animals and plants, including the imperiled California gnatcatcher, coastal cactus wren, more than 20 other vertebrate species that are candidates for federal protection, several invertebrate candidate species, as well as nearly 100 plant species that are of special conservation concern.

The first NCCP was initiated with appointment of a scientific review panel enjoined to outline a conservation strategy for the coastal sage scrub ecosystem. Although the scientific review panel collected extensive information on the coastal sage scrub community and its constituent plant and animal species, it was not able to produce final scientifically defensible guidelines for long-range planning purposes because the available database was limited. Instead, the scientific review panel assisted in producing interim planning rules that institutionalize several of the recommendations in this chapter, including the interim protection of habitat crucial for survival until recovery planning is in place.

The scientific review panel concluded that federal protection of the California gnatcatcher alone would not be sufficient to confer protection to other species at risk in the coastal sage scrub community. Indeed, it is highly likely that prohibition of take of the gnatcatcher under Section 9 of the Endangered Species Act would not even serve to ensure the persistence of that species. Its highly disjunct distribution demands conservation of ample amounts of coastal sage scrub habitat, including habitat that is not currently occupied by the gnatcatcher, as well as conservation of other habitat types to provide landscape corridors for dispersal by the species. In the absence of a regional, community-level conservation plan, additional listings of coastal sage-scrub species would be inevitable despite the listing of the California gnatcatcher.

Toward the development of a community-level conservation plan and focusing on three target species of vertebrates (the California gnatcatcher, the coastal cactus wren, and the orange-throated whiptail lizard), the distributions of which embrace the majority of the planning area, the scientific review panel examined existing data and suggested additional information to be gathered that would shed light on the coastal sage scrub community and the many species it supports. This multiple-species planning effort attempted to use the best scientific methods available to:


Define the management planning region;


Identify subregional planning areas that consider landscape features, biological factors, and political jurisdictions;


Describe an interim conservation planning framework for developing a viable system of subregional reserves;


Recommend appropriate techniques for gathering baseline field data and their analysis;


Recommend research and monitoring activities to assist in subregional conservation planning for individual areas; and


Recommend a selection process for a subcommittee of specialists to report on the best available techniques for restoration and management.

Some data available in some portions of the planning area were of substantial immediate value to subregional planning, but the amounts of information then available by and large were not adequate to identify the physical characteristics of management areas necessary to protect ecosystem functioning through time, to identify minimum viable population sizes for target species, or to describe effective landscape corridors that would facilitate ecological interaction and gene flow among organisms that occupy the coastal sage scrub community. The scientific review panel therefore described a research program focusing on six interactive research tasks.


Biogeography and inventory of coastal sage scrub. The basic extent and distribution of coastal sage scrub vegetation and its constituent species are to be adequately mapped for the region and for each subregion.


Trends in biodiversity. Monitoring of indicator taxa (such as coastal sage shrub dependent birds, small mammals, and butterflies) will help to assess the ongoing success of coastal sage shrub community conservation efforts. Relationships between species richness/composition and habitat patch area, and the effects of isolation are to be investigated in sampling programs. These sampling programs must include surveys for species richness and composition within a carefully selected series of coastal sage shrub patches in each subregion.


Dispersal characteristics and landscape corridor use. Data from several locations within the planning region are to be gathered during both breeding and nonbreeding seasons on target species, top predators, coyotes, and representative small mammals and invertebrates.


Demography and population viability analysis. Time-series data on the two target species of birds are to be gathered in at least half the subregions and from representative physical circumstances that span those found across the regional distributions of the species. Data must include territory size, time budgets, reproductive success, survivorship, emigration and immigration, with separate data obtained both for males and females where possible. Population viability analyses are to be carried out for sample populations and metapopulations, and should consider connectivity and environmental effects.


Surveys and autecological studies of sensitive animals and plants. Basic information on the location, abundance, distribution, and natural history of vertebrate and invertebrate candidate species for federal protection and coastal sage shrub associated plant species of special concern are to be gathered from select sites throughout the planning region.


Genetic studies. The maintenance of genetic variation is critical to the long-term viability of species inhabiting coastal sage shrub and its assessment is an important aspect of population monitoring.

The NCCP planning area is in lands that have been greatly affected by human activities. Natural and anthropogenic disturbances will continue; many of those disturbances will reduce the capacity of coastal sage scrub habitats to support many species of concern. Areas designated as reserves thus are unlikely to be self-sustaining (that is, provide for natural, dynamic ecosystem processes) or to be capable of maintaining viable populations of target species without active management. The ability of individual patches of coastal sage scrub habitat to be effectively managed over the long term will be a critical factor in prioritizing of conservation efforts.

For these reasons and in recognition of the critical role of restoration activities in the Natural Communities Conservation Planning Program, the scientific review panel encouraged the immediate creation of a committee to address central issues in management and restoration to focus on


Exotic species control, including animals and plants.


Recreational use of coastal sage scrub and other open space reserve areas, including identification of suitable low impact recreational pursuits consistent with preservation goals.


The role of fire in natural ecosystem dynamics and processes, including the application of managed burns and the control of ignitions of accidental and vandal origin.


Identification of restoration unit sizes, including identification of maximum areas that are restorable using current techniques. A focus on patch enlargement techniques is advised.


Identification of coastal sage scrub responses to soil conditions in restoration efforts, with focus on soil structure, soil nutrient levels, organic matter content, water holding capacity, and soil compaction.


Identification of appropriate seeding, outplanting, and irrigation techniques with focuses on proper mixes of species, seeding techniques, and timing of applications of seed and irrigation.


Identification of techniques to encourage native herbaceous species and to discourage the establishment of exotic species.


Establishment of realistic success criteria to evaluate management and restoration efforts considering sage species diversity and cover, and use by target species.

During the interim period while data are being gathered, land-use planning will continue. Draft conservation planning guidelines therefore were published that describe short-term land use restrictions for a limited period based on recommendations from the scientific review panel. Those recommendations were meant to allow some development without foreclosing future conservation options, and three key objectives are to be met during the interim data acquisition period.

First, development is to be limited to 5% or less of the landscape that is occupied by coastal sage scrub and its resident species. Development should also strive not to disproportionally affect any ''environmental subunit" (defined by vegetational subcommunity, elevation, slope, aspect, latitude, distance from coast, and substrate) within each subregional NCCP planning area.

Second, to the extent feasible, development is to avoid likely "hotspots" of biotic diversity (based on habitat patch size and isolation).

Third, development is not to sever extant open space landscape linkages between biodiversity hotspots.

Because threats to the persistence of species were viewed as so pressing, conservation planning should result in no net loss of habitat value, defined as the ability of the coastal sage scrub habitat to support target species in a subregion over the long term. Expected incremental losses of habitat therefore must be mitigated with habitat restoration activities and effective management planning.

In addition, the scientific review panel believed that long-term NCCP goals were to be best met where six tenets of conservation biology are incorporated at all spatial scales in regional and subregional planning.


Species that are well distributed across their native ranges are less susceptible to extinction than are species confined to small portions of their ranges.


Large blocks of habitat containing large populations of the target species are superior to small blocks of habitat containing small populations.


Blocks of habitat that are close together are better than blocks far apart.


Habitat that occurs in blocks that are less fragmented internally is preferable to habitat that is internally fragmented.


Interconnected blocks of habitat serve conservation purposes better than isolated blocks, and habitat corridors or linkages function better when the habitat within them resembles habitat that is preferred by target species.


Blocks of habitat that are roadless or otherwise inaccessible to humans serve to better conserve many target species than do roaded and accessible habitat blocks.

To differentiate between habitat areas that are likely to be more rather than less important to long-term planning, a habitat-evaluation process was developed.

Habitats are to be differentiated into three categories. Those having higher potential conservation value need to be identified early in the planning process and protected from habitat loss and fragmentation while planning is under way. The methodology described in the guidelines places 50% of the coastal sage scrub in each planning subregion in the higher potential value category. Habitats with intermediate potential value are those lands that probably cannot be managed as independent reserves, but which by virtue of high quality or proximity or linkage to higher value habitats should be treated as potentially significant for subregional conservation planning. Habitats of lower potential value are those left after the higher and intermediate value areas have been identified and include small, isolated patches, the loss of which would probably not affect the long-term viability of the target species or other species of concern. Overall, an estimated 10%-25% of the coastal sage shrub in a subregion would fall into the lower potential value category. For the ranking approach to interim habitat loss to function, it is important that a significant amount of land be classed as lower value. The criteria for identifying higher and intermediate value land are to be adapted to local conditions.

Each planning subregion needs to show interim protection for higher potential value lands on a map, using a step-down process. Large, dense areas of coastal sage scrub are the higher potential value lands. Natural lands that occur in linkages, that are close to possible higher value areas, or that have high species richness are considered intermediate potential value lands. Remaining coastal sage scrub is considered to have lower potential value. A guideline policy for local government treatment of the higher, intermediate, and lower potential value lands during the interim period includes six assessment criteria that address (in order) the presence of natural vegetation, the presence of coastal sage scrub, the size of the scrub patch, its proximity to higher value lands, its role as a potential landscape linkage or corridor, and the densities of target species.

Habitat-Related Standards

Several habitat-related features of the ESA differ without basis in science. Prominent among these are standards applicable to the protection of plants, and to the determination of jeopardy and modification of critical habitat. As noted earlier, Section 9 fails to protect endangered plants from habitat modification to the same degree that it protects animals. Plants, like animals, require places to live and space for dispersal of their offspring. Plants include, for example, species isolated in unique environments and others that disperse pollen, spores, and seeds over wide areas. The biological differences between animals and plants underlying their taxonomic separation offer no scientific reason for lesser protection of plants, nor do their importance to scientific and other research.

Under sections 7, 9, and 10, FWS and NMFS are required to determine whether federal actions or private actions that are federally permitted (Section 7) and nonfederal activities (sections 9 and 10) present an unacceptable threat to listed species and their habitats. Although the administrative processes for making these determinations differ, these judgments are not distinguishable as matters of biology and physics. Two scientific issues need very careful attention in the application of the Endangered Species Act. The first concerns the differences and similarities between standards for public and private lands and actions. The second concerns the relationship between survival and recovery.

Public and Private Lands and Actions

Section 7 requires that federal and federally permitted actions do not jeopardize listed species; Section 9 requires that private parties not take them. The biological and physical requirements of species—including endangered and threatened species—do not vary according to the ownership of the habitats that they occupy. The requirement of sockeye salmon for clean, cool water and of clapper rails for safe nesting sites are not changed if they live on public or private land. A tidal marsh that provides habitat for endangered species will be equally affected if it is filled by a public agency for a public facility, such as a sports complex or a marina, or by a private agency for a private facility, such as a shopping center or a hotel. Therefore, there is no biological reason to have different standards for determination of "jeopardy," "survival," or ''recovery" on public and on private lands.

This observation becomes particularly relevant to resolution of the controversy surrounding the application of sections 9 and 10 to habitat modification on nonfederal lands. Whether Congress intended sections 9 and 10 to regulate habitat modification on private lands is a legal question, but there is no scientific question that a species might be as effectively jeopardized by habitat development as by overharvest and that an endangered species program regulating habitat modification only on federal lands will fail to protect many endangered species. The committee also recognizes that public agencies and individual public servants on public lands behave differently from private landowners, both corporate and individual, on private lands, because their rewards, incentives, and disincentives are different.5 Therefore, requirements applied equally on private and public lands will not necessarily provide the same degree of protection, although the biological standards or criteria on which the regulations are based are the same. It follows, then, that different mechanisms for avoiding endangerment and achieving recovery on public and private lands are probably needed.

Survival and Recovery

The act and its regulations distinguish between species survival and recovery to determine jeopardy to species and adverse modification of their critical habitat. Both determinations present biologists with judgments that differ in degree, not in kind. Survival and recovery are points on a continuum. Anything that jeopardizes species recovery makes survival less likely, although it might still be likely over the short term; to make survival very likely, recovery must be ensured. Ensuring survival for a short period is not equivalent to promoting recovery, especially for long-lived species like razorback chub in Lake Mead, where populations can persist for many years without reproduction. The difficulty arises when the concept of short-term survival is applied to determinations of jeopardy and of effect on critical habitat with respect to federal actions, such as development of water resources, which often have long-term, if not irreversible, effects. A decision, for example, to allow destruction of one of three remaining habitats for a species—predicated on the assumption that it will jeopardize only recovery and not survival—requires biologists to ignore threats to long-term survival by irreversible actions. The impacts of activities with long-term or irreversible consequences should be evaluated under a long-term standard. The relationship between survival and recovery should be kept clearly in the minds of those who make and implement decisions. It is important to make estimates of the probability of survival for given periods to help keep that relationship in mind.

Conclusions and Recommendations

Habitat conservation and recovery planning are essential components of any program to protect endangered species. To prevent delay and to allow immediate action to protect endangered species, survival habitat should be designated for a period necessary to develop a recovery plan.

There is no biological or physical reason that standards relating to habitat protection, survival, and recovery should differ for plants and animals and for public and private lands. The degree to which public and private entities should bear the responsibilities of the Endangered Species Act is a policy decision. But there is no escaping the scientific conclusions that all species have certain biological and physical requirements no matter who owns the habitats, and that public and private landowners do not always respond in the same way to laws, regulations, and other incentives and disincentives.

Finally, survival and recovery are not equivalent standards, although they are related. Clearly, if a species does not survive, it cannot recover. It is less obvious, but still true, that any action that jeopardizes recovery also decreases the probability of long-term survival. To permit a rational evaluation of survival and recovery goals, it is important to provide estimates of probabilities of achieving various goals over various periods, and the periods should be expressed both in years and in generation times of the organism of concern.6 It is also important that evaluation of long-term and irreversible impacts be conducted in terms of long-term recovery of the species.

The committee recommends that the impacts of activities with long-term or irreversible consequences be evaluated under a long-term standard.

The committee further recommends that the relationship between survival and recovery be kept clearly in the minds of those who make and implement regulations. To further that end, the committee recommends that determinations of survival and recovery contain good-faith estimates of the probability of survival for given periods, perhaps 5, 10, and 100 years, as well as the probability of survival in numbers of generations, perhaps 5, 10, and 100.

The committee endorses regionally based, negotiated approaches to the development of habitat conservation plans. Guidance from FWS for the development of such plans should include advice on the development of biological data, such as demographic and genetic analyses, habitat requirements of the species involved, reserve design, and monitoring, and it should also include advice on descriptions of management options and application of risk analyses in consideration of alternatives.


  • Andrewartha, H.G., and L.C. Birch. 1954. The Distribution and Abundance of Animals. Chicago: University of Chicago Press.
  • Beatley, T. 1994. Habitat Conservation Planning. Austin, Tex.: University of Texas Press.
  • Clements, F.E., and V.E. Shelford. 1939. Bio-Ecology. New York: John Wiley & Sons.
  • DOI (U.S. Department of the Interior) Office of the Inspector General. 1990. Audit Report: The Endangered Species Program. U.S. Department of the Interior, Washington, D.C.
  • Elton, C. 1927. Animal Ecology. London: Sedgwick and Jackson.
  • FWS (U.S. Fish and Wildlife Service). 1990. Interim National Conservation Planning Guidelines. U.S. Department of the Interior, U.S. Fish and Wildlife Service, Washington, D.C.
  • FWS (U.S. Fish and Wildlife Service). 1992. Report to Congress: Endangered and Threatened Species Recovery Program. U.S. Department of the Interior, U.S. Fish and Wildlife Service, Washington, D.C.
  • FWS (U.S. Fish and Wildlife Service). 1994. Preliminary Draft Handbook for Habitat Conservation Planning and Incidental Take Permit Processing. U.S. Department of the Interior, U.S. Fish and Wildlife Service, Washington, D.C.
  • Gilbert, L.E. 1980. Food web organization and the conservation of neotropical diversity. Pages 11-33 in M.E. Soulé, editor; and B.A. Wilcox, editor. , eds. Conservation Biology: An Evolutionary-Ecological Perspective. Sunderland, Mass.: Sinauer Associates.
  • Groombridge, B., editor. , ed. 1992. Global Biodiversity: Status of the Earth's Living Resources. New York: Chapman and Hall.
  • Jackson, T.C. 1992. All creatures great and small. Legal Times, Dec. 7, pp.20-23.
  • Jensen, D.B., M.S. Torn, and J. Harte. 1993. In Our Own Hands: A Strategy for Conserving California's Biodiversity. Berkeley, Calif.: University of California Press.
  • Jones, G.E. 1987. The Conservation of Ecosystems and Species. New York: Croom Helm.
  • Krebs, C.J. 1985. Ecology: Experimental Analysis of Distribution and Abundance. 3rd Ed. New York: Harper & Row.
  • Mann, C.C., and M.L. Plummer. 1995. Noah's Choice: The Future of Endangered Species. New York: Alfred A. Knopf.
  • McArthur, R.H., and E.O. Wilson. 1967. The Theory of Island Biogeography. Princeton, N.J.: Princeton University Press.
  • McNaughton, S.J. 1989. Ecosystems and conservation in the twenty-first century. Pp 109-120 in Conservation for the Twenty-First Century, D. Western, editor; and M.C. Pearl, editor. , eds. New York: Oxford University Press.
  • NRC (National Research Council). 1993. Setting Priorities for Land Conservation. Washington, D.C.: National Academy Press.
  • Pianka, E. 1978. Evolutionary Ecology, 2nd Ed., editor. New York: Harper & Row.
  • Tear, T.H., J.M Scott, P.H. Hayward, and B. Griffith. 1993. Status and prospects for success of the Endangered Species Act: A look at recovery plans. Science 262:976-977. [PubMed: 17782035]
  • Thornton, R.D. 1991. Searching for consensus and predictability: Habitat conservation planning under the Endangered Species Act of 1973. Environ. Law 21:605-656.
  • Van Horne, B. 1983. Density as a misleading indicator of habitat quality. J. Wildl. Mgmt. 47:893-901.
  • Whitford, P.B. 1949. Distribution of woodland plants in relation to succession and clonal growth. Ecology 30:199-208.
  • Wilson, E.O. 1992. The Diversity of Life. Cambridge, Mass.: Harvard University Press.



The Supreme Court recently reviewed Babbitt versus Sweet Home Chapter of Communities for a Greater Oregon. The case focused on FWS regulations concerning the act's prohibition against taking an endangered species, in this case, the northern spotted owl. Take is defined in the ESA to include harm, and FWS has defined harm to include significant habitat modification that adversely affects an endangered species. The U.S. Court of Appeals for the District of Columbia ruled in a split decision that "the Service's definition of 'harm' was not clearly authorized by Congress nor a 'reasonable interpretation' of the statute" (1994 U.S. App. LEXIS 4341); the Supreme Court decided 6-3 that Secretary Babbitt reasonably construed Congress' intent when he defined "harm" to include habitat modification (115 S. Ct. 2407).


We do not specify a precise time, because the length of survival time expected should be based on knowledge of the species' biology, including its generation time.


H.R. Rep. No. 835, 97th. Congress, 2nd session 31, reprinted in 1982 U.S. Code Congressional and Administrative News 2807, 2831.


From 1982 to July 1994, FWS issued 33 incidental take permits and 12 permit amendments, but many of those were very small projects rather than full-scale HCPs. Approximately 130 HCPs and permit applications are now in various stages of development (FWS, 1994), most of them small in scope as well.


For example, Mann and Plummer (1995) described the destruction by private landowners of habitat on their land that could support endangered species so that they can avoid the prohibitions of Section 9 or avoid the need for a Section 10(a) permit for incidental take.


Estimates of periods in years are important for planning of human activities, and generation times are important to provide biological realism to the estimates.

Copyright 1995 by the National Academy of Sciences. All rights reserved.
Bookshelf ID: NBK232378


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